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Add native USB CDC broker transport

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Commander1024
2026-08-23 00:47:56 +02:00
parent 6793f6bcc2
commit aa5fa207b6
11 changed files with 1394 additions and 9 deletions
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wiring.md
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@@ -59,7 +59,7 @@ GPIO9 ────────────> OFF
UART1 is used for the external RS-232 data path. GPIO17 and GPIO18 are the ESP32-S3's conventional `U1TXD` and `U1RXD` pins. GPIO15 and GPIO16 are physically adjacent to them on header J1 and are routed to UART1 RTS and CTS through the ESP32-S3 GPIO matrix.
The GPIO matrix means GPIO15 and GPIO16 can serve UART1 even though their fixed-function labels mention UART0 RTS and CTS. UART0 logging remains on GPIO43 and GPIO44 through the board's USB-to-UART bridge. GPIO19 and GPIO20 remain free for future native USB CDC-ACM support.
The GPIO matrix means GPIO15 and GPIO16 can serve UART1 even though their fixed-function labels mention UART0 RTS and CTS. UART0 logging remains on GPIO43 and GPIO44 through the board's USB-to-UART bridge. GPIO19 and GPIO20 are reserved for the current native USB CDC-ACM transport.
RTS/CTS flow control will be configurable. When enabled, the UART peripheral can handle it in hardware so backpressure does not depend on application-task scheduling. When disabled, firmware must place the output signals in compatible idle states.
@@ -88,6 +88,19 @@ The breakout's `OFF` pin is connected to the MAX3243 active-low `!FORCEOFF` inpu
GPIO8 and GPIO9 are not adjacent on the official J1 header. GPIO3 and GPIO46 lie between them and are boot-strapping pins, so follow the printed GPIO labels instead of counting header positions.
### Development and native USB connectors
This hardware profile uses both USB controllers for different purposes:
| DevKit connector | ESP32-S3 path | Typical Linux device | Purpose |
|---|---|---|---|
| `USB-to-UART` | UART0 on GPIO43/44 through the board's bridge chip | `/dev/ttyUSB*` | Firmware upload, logs, and `serial-tool>` development console |
| `USB` | Native USB OTG, GPIO19 `D-` and GPIO20 `D+` | `/dev/ttyACM*` | CDC-ACM client connected to the serial-session broker |
GPIO19 and GPIO20 are connected to the native USB connector and must not be assigned to the MAX3243, display, buttons, or other peripherals while USB CDC is enabled. Both connectors may be attached to the development host during testing so UART0 logs remain available while native USB carries broker data. Compatible DevKit clones can differ in connector labels and power-path design; verify the board schematic before assuming that two attached cables cannot back-power one another.
CDC DTR indicates that the host application has opened the native serial port. It controls the lifetime of the `usb-cdc` broker client but is not directly forwarded to the physical DE-9 DTR output. Physical DTR follows the firmware's `serial` configuration. Likewise, host CDC RTS is status information only; GPIO15/DE-9 RTS remains dedicated to UART1 receive flow control when `flow=rts-cts` is enabled.
## Phase 0 loopback tests
The hardware-characterization firmware never starts a test automatically. Wire exactly one configuration below while the board is powered down, inspect the connections, power it again, and then invoke the corresponding console command.